title: Determination of the exact molecular requirements for type 1 angiotensin receptor epidermal growth factor receptor transactivation and cardiomyocyte hypertrophy.
abstract: Major interest surrounds how angiotensin II triggers cardiac hypertrophy via epidermal growth factor receptor transactivation. G protein-mediated transduction, angiotensin type 1 receptor phosphorylation at tyrosine 319, and β-arrestin-dependent scaffolding have been suggested, yet the mechanism remains controversial. We examined these pathways in the most reductionist model of cardiomyocyte growth, neonatal ventricular cardiomyocytes. Analysis with [(32)P]-labeled cardiomyocytes, wild-type and [Y319A] angiotensin type 1 receptor immunoprecipitation and phosphorimaging, phosphopeptide analysis, and antiphosphotyrosine blotting provided no evidence for tyrosine phosphorylation at Y319 or indeed of the receptor, and mutation of Y319 (to A/F) did not prevent either epidermal growth factor receptor transactivation in COS-7 cells or cardiomyocyte hypertrophy. Instead, we demonstrate that transactivation and cardiomyocyte hypertrophy are completely abrogated by loss of G-protein coupling, whereas a constitutively active angiotensin type 1 receptor mutant was sufficient to trigger transactivation and growth in the absence of ligand. These results were supported by the failure of the β-arrestin-biased ligand SII angiotensin II to transactivate epidermal growth factor receptor or promote hypertrophy, whereas a β-arrestin-uncoupled receptor retained these properties. We also found angiotensin II-mediated cardiomyocyte hypertrophy to be attenuated by a disintegrin and metalloprotease inhibition. Thus, G-protein coupling, and not Y319 phosphorylation or β-arrestin scaffolding, is required for epidermal growth factor receptor transactivation and cardiomyocyte hypertrophy via the angiotensin type 1 receptor.
authors.affiliation: Baker IDI Heart and Diabetes Institute, Prahran, Victoria, Australia. nicola.smith@bio.gla.ac.uk
authors.forename: Nicola J
authors.initials: NJ
authors.lastname: Smith
authors.forename: Hsiu-Wen
authors.initials: HW
authors.lastname: Chan
authors.forename: Hongwei
authors.initials: H
authors.lastname: Qian
authors.forename: Allison M
authors.initials: AM
authors.lastname: Bourne
authors.forename: Katherine M
authors.initials: KM
authors.lastname: Hannan
authors.forename: Fiona J
authors.initials: FJ
authors.lastname: Warner
authors.forename: Rebecca H
authors.initials: RH
authors.lastname: Ritchie
authors.forename: Richard B
authors.initials: RB
authors.lastname: Pearson
authors.forename: Ross D
authors.initials: RD
authors.lastname: Hannan
authors.forename: Walter G
authors.initials: WG
authors.lastname: Thomas
mesh_terms: D051722:ADAM Proteins / Q000378:metabolism; D000704:Analysis of Variance; D000818:Animals; D019390:Arrestins / Q000235:genetics / Q000378:metabolism; D019556:COS Cells; D006332:Cardiomegaly / Q000235:genetics / Q000378:metabolism*; D049108:Cell Enlargement; D002478:Cells, Cultured; D002522:Chlorocebus aethiops; D066246:ErbB Receptors / Q000235:genetics / Q000378:metabolism*; D047468:Immunoprecipitation; D020782:Matrix Metalloproteinases / Q000378:metabolism; D032383:Myocytes, Cardiac / Q000378:metabolism*; D010766:Phosphorylation; D044140:Receptor, Angiotensin, Type 1 / Q000235:genetics / Q000378:metabolism*; D000071557:beta-Arrestins
chemical_list: D019390:Arrestins; D044140:Receptor, Angiotensin, Type 1; D000071557:beta-Arrestins; D066246:ErbB Receptors; D051722:ADAM Proteins; D020782:Matrix Metalloproteinases